The data of 302 highway bridge catastrophic collapses occurring in China between 2000 and 2014 due to human causes were collected and statistical analyses were conducted from various viewpoints including accident stages (during construction or service), casualties (death or injury), location, time, life span, bridge type, and primary causes behind the accidents. Six representative collapse cases were expounded on to find out their individual peculiarities. These cases encapsulated serious problems in Chinese highway bridge engineering, including design, construction, maintenance, and management, among others. A concise review of highway bridge collapses due to human causes in China was presented. Some typical abnormal phenomena, such as those concerning entities involved in the Chinese highway bridge engineering industry, were analyzed and highlighted. Suggestions were put forward to urge all related parties to obey rules and laws to reduce and avoid bridge collapse accidents. The lessons from the...

The nonlinear flutter featured by the limit cycle oscillation (LCO) is a typical aeroelastic phenomenon for bluff decks and/or streamlined decks at large incidence angles. In this study, the flutter characteristics of a streamlined deck were investigated by using comprehensive wind-tunnel tests, and a nonlinear mathematical model was introduced to model the aeroelastic behavior of the nonlinear torsional flutter oscillation. The nonlinear aerodynamic force is the major source of the nonlinear flutter. The nonlinear flutter LCO corresponds to a state in which the energy absorbed by the linear damping and the energy dissipated by the nonlinear damping are balanced within an oscillation period. On the basis of the instantaneous amplitude and instantaneous frequency calculated by using the normalized Hilbert transform, a system identification method was developed to simultaneously extract the linear and nonlinear aerodynamic parameters. The efficacy of the nonlinear mathematical model and the identification accuracy of aerodynamic parameters were validated by two examples. The sensitivities of aerodynamic parameters to the signal length were studied, and the corresponding causes were revealed. The linear aerodynamic damping parameter and structural damping ratio are the dominant parameters for determining the critical flutter wind speed. For the nonlinear torsional flutter, a practical approach was proposed to predict the critical reduced wind speeds and the LCO amplitudes with different structural damping ratios, and its accuracy was verified by comparing the experimental results.